X-ray-induced adenocarcinomas in the small bowels of outbred Lewis Brown Norway and Holtzman rats contained significantly lower concentrations of adenosine 3',5'-cyclic monophosphate than did normal ...rat intestinal tissue. No significant differences were observed between the intracellular concentrations of the nucleotide in the normal rat small bowel and those occurring in normal-appearing intestinal tissue exposed to tumor induction conditions.
Enhanced lipid peroxidation potential was measured in Holtzman rat colon tumors induced by chronic subcutaneous injection of 1,2-dimethyl-hydrazine as compared with normal colonic tissue. The ...peroxidation potentials were determined in the mitochondrial cellular components by measuring the ferrous-ascorbate induced formation of malondialdehyde. The tumor mitochondria were found to peroxidize at a rate 8-10-fold higher than the comparable normal tissue components. In addition, we found that the mitochondria from the cancer cells exhibited reduced NADH-cytochrome c reductase activity. These observations suggest an involvement of non-enzymatic free radical flux in DMH-induced carcinogenesis, which may be the result of structurally altered mitochondrial membranes.
The activities of three antioxidant enzymes, Superoxide dismutase, catalase, and glutathione peroxidase, were monitored in isolated human renal adenocarcinoma tissues and in cultured human renal ...adenocarcinoma cells. The results were compared to the activities of these enzymes in the proposed cell of origin, isolated human proximal tubular tissues, and cultured proximal tubular epithelial cells. Strong modulation of these enzymes by culture conditions was observed in normal cells but not in carcinoma cells. Low levels of cellular lipid peroxidation, as assessed by levels of malondialdehyde (MDA), were observed in adenocarcinoma cells under the culture conditions tested with one exception: greatly elevated MDA was observed in renal adenocarcinoma cells grown on plastic in serum-free, chemically defined medium. This increased lipid peroxidation correlated with a loss of cell viability under these conditions.
